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HOME> Expert Assessments>Hazards Outlook

U.S. Hazards Outlook - Made January 16, 2017

 Days 3-7Days 8-14Prob. Days 8-14
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Categorical Outlooks
Experimental Probabilistic Outlooks (Information)

Valid Thursday January 19, 2017 to Monday January 30, 2017

US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EST January 16 2017

Synopsis: An area of upper-level pressure and enhanced onshore flow is likely to persist across the western U.S. during the next week, while multiple low pressure systems advance across the central and eastern U.S. During Week-2, a pattern change is expected with an area of upper-level high pressure developing near the West Coast. Arctic high pressure is forecast to remain centered over mainland Alaska through the weekend, while a strong surface low is expected to enter the Bering Sea by early next week.

Hazards Detailed Summary

For Thursday January 19 - Monday January 23: A series of upper-level troughs, strong onshore flow, and enhanced Pacific moisture are likely to result in periods of heavy precipitation (rain and high-elevation snow) across southwest Oregon, California, southwest Utah, and Arizona during this period. Deterministic model solutions indicate that the heaviest precipitation (5 to 10 inches, liquid equivalent) is likely across the orographically favored coastal ranges and Sierra Mountains of California. Snow levels are generally expected to lower by early next week across the western U.S. as 500-hpa heights decrease with snow levels potentially below 5,000 feet across Arizona on Jan 23. Period of high winds (gusts above 50 mph) are also forecast across from the western U.S east to the southern high Plains during this period.

Although the shortwave troughs, emerging from the western U.S., are expected to dampen as they progress into mean ridging aloft over the eastern U.S., there is a signal for heavy rain across the southeastern U.S. due to abundant low-level moisture for January. Therefore, periods of heavy rain are forecast from the Gulf Coast north to the Tennessee Valley and southern Appalachians from January 19 to 22. Model guidance indicates that 96-hour total rainfall amounts could locally exceed 5 inches across the outlined area for heavy rain.

On January 21, the exit region of a strong mid-level jet, coinciding with moderate instability and high low-level moisture, is expected to support severe thunderstorms across parts of the southeastern U.S. The severe weather hazard area for the southeastern U.S. is expected to be extended through Jan 22 in subsequent outlooks. The unusual aspect of the storminess across the central and eastern U.S. will be the lack of winter weather associated with the low pressure systems, given the absence of cold air.

Much below-normal temperatures are posted for mainland Alaska through Jan 22, where the 6z GFS ensemble mean indicates temperatures averaging more than 20 degrees F below normal. The deterministic models indicate that a potent low pressure system (around 964-hpa) will enter the Bering Sea and bring high winds (50 knots or greater) to the Aleutians and Alaska Peninsula on Jan 23.

For Tuesday January 24 - Monday January 30: The ensemble means are in good agreement and remain consistent that a major pattern change occurs during the final week of January. An upper-level ridge is expected to build near the West Coast, resulting in a much drier pattern for the Pacific Northwest and northern California. Meanwhile, a full latitude trough is forecast to extend from Hudson Bay to the central U.S. This longwave pattern is expected to favor a trend towards more seasonal temperatures across the central and eventually the eastern U.S. later in Week-2.

Surface high pressure is expected to become centered over the Great Basin early in the Week-2 period. A slight risk of much below-normal temperatures is posted for parts of the interior West where strong low-level inversions are most likely.

An upper-level trough, located south of the Aleutians, favors multiple low pressure systems with onshore flow affecting southeast Alaska and the Alaska Panhandle during Week-2. Heavy precipitation (rain and high-elevation snow with amounts of more than 1.5 inches per 24 hours) and high winds (speeds greater than 50 knots) are posted for these areas throughout the period.

According to the latest U.S. Drought Monitor (USDM) valid on January 10, the coverage of severe or greater drought for the CONUS decreased from 8.63 to 7.96%. One to two category improvements were made to the drought areas across parts of California and Nevada from the previous week.

Forecaster: Brad Pugh

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Please consult local NWS Forecast Offices for short range forecasts and region-specific information.